Stephanorhinus kirchbergensis: A Rhinoceros from the Pleistocene of Romania.

Three species of Rhinoceros are known from the Middle-to-Late Pleistocene of Romania, the Woolly Rhinoceros, Coelodonta antiquitatis, a cold-adapted species associated with the various glacial phases, the Narrow-nosed rhinoceros, or Steppe Rhinoceros, Stephanorhinus hemitoechus, a species associated with the warmer, interglacial phases, and Merck's Rhinoceros, Stephanorhinus kirchbergensis, a larger species which may have reached as much as three tonnes, making it larger than the White Rhinoceros, Ceratotherium simum, the largest extant Rhinoceros species. Merck's Rhinoceros also appears to have favoured warmer phases, and possibly to have been restricted to the Eemian Interglacial (between 130 000 and 150 000 years ago), although specimens have been found from Siberia which apparently lived alongside Woolly Rhinoceroses, suggesting the species may have been longer lived more tolerant of climatic variation than it is generally given credit for.

In a paper published in the North-Western Journal of Zoology on 15 June 2026, Vlad Codrea of the Paleotheriology and Quaternary Geology Laboratory at Babeș-Bolyai University, the Department of Natural Sciences at Mureș County Museum, the Department of Natural History at Țării Crișurilor Museum, and the Emil Racoviță Speleological Institute, and Aurelian Popescu of the Department of Natural Sciences at the Museum of Oltenia Craiova, describe a partial Rhinoceros mandible from Dolj County in southwestern Romania. 

The mandible was discovered by English engineer William Heerlein Lindley, who was working on a water supply system for the city of Craiova, which had undergone a period of rapid expansion during the late nineteenth century, leaving the system of wells which had traditionally provided water for its residents wholly inadequate. It is unclear exactly where Lindley found the mandible, but it probably came from the Upper Terrace of the Jui River Basin, which reaches its greatest width to the east of Craiova, and where Lindley carried out considerable work, channelling water from natural springs into a system of cast-iron pipes to supply the city. The Upper Terrace has also yielded Woolly Mammoth, Mammuthus primigenius, Woolly Rhinoceros, Coelodonta antiquitatis, and Irish Elk, Megaloceros giganteus, fossils, and is considered to be Late Pleistocene in age.

Location of the municipality of Craiova. Codrea & Popescu (2026).

Lindley gave the mandible to Alexandru and Aristia Aman, who had a collection of art, antiquities, and books, which in turn was passed to the Olteniei Museum in Craiova in the 1950s, with the specimen becoming part of that museum's natural history collection.

The specimen is the rear part of the mandible of a large Perissodactyl, with the anterior portion broken off, a broken area on the anterior edge of the coronoid process. This broken area makes it hard to judge the  elevation of the anterior edge of the vertical branch of the mandible. The teeth have also been broken from the jaw, but this is recent damage, probably caused during its excavation.

Right half mandible from the Malu Mare area of Dolj County, Romanina, in (a) lateral buccal view, (b) lateral lingual view, and (c) upper view. Codrea & Popescu (2026).

The damage to the jaw removes many of the diagnostic features used when classifying Perissodactyls, though its large size rules out anything but a large Rhinoceros, while still being too small for the truly enormous Elasmotherium. It also has a nutrient foramina on the ventral side of the symphysis, a feature associated with Merck's Rhinoceros, leading Codrea and Popescu to conclude that it should be assigned to this species.

While the teeth of the specimen are missing, they were clearly all fully erupted, indicating that it was an adult at time of death. It was probably of about average size for a specimen of Stephanorhinus kirchbergensis. The exact age of the specimen is impossible to know, given the circumstances of its discovery. If it does come from the sediments Lindley excavated at Malu Mare when laying his pipeline, then it would be the oldest known Rhinoceros from Romania, as well as having come from deposits which also yielded cold-adapted species such as Woolly Rhinoceros, Woolly Mammoth, and Irish Elk, although it is possible that Lindley discovered it elsewhere, so this cannot be asserted with any confidence.

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Uragasaurus kalasinensis: A new species of Mamenchisaurid Sauropod from the Late Jurassic of northeastern Thailand.

The Mamenchisaurids were a group of non-Neosauropod Sauropods (i.e. outside the largest grouping of Sauropods) which formed a significant part of the fauna of East Asia during the Middle and Late Jurassic. They can be distinguished by highly pneumatised and elongated cervical vertebrae, as well as procoelous vertebrae on the front part of the caudal spine (procoelous vertebrae have a convex forward disk and a concave rear disk), which were distinctive during the Jurassic, but evolved convergently in several Neosauropod groups during the Cretaceous. 

Most known Mamenchisaurids come from China, and for a long time they were thought to be restricted to that country. However, in 2005 fragmentary remains attributed to the group were recovered from the Middle to Late Jurassic Khlong Min Formation of Krabi Province in southern Thailand. In 2013, further fragmentary remains were found in the Late Jurassic to Early Cretaceous Phu Kradung Formation of northeastern Thailand, and in 2019 a new species of Mamenchisaurid, Wamweracaudia keranjei, was described on the basis of a partial skeleton from the Late Jurassic Tendaguru Formation of southeastern Tanzania, establishing the presence of the group in Africa.

In a paper published in the journal Scientific Reports on 8 July 2026, Apirut Nilpanapan of the Department of Biology at Mahasarakham University, Sita Manitkoon of the Palaeontological Research and Education Centre and Vertebrate Palaeontology and Evolution Research Unit at Mahasarakham University, Varavudh Suteethorn of the Khon Kaen Geopark Association, and Komsorn Lauprasert also of the Department of Biology and Evolution Research Unit at Mahasarakham University, describe a new species of Mamenchisaurid Sauropod from the Phu Kradung Formation of northeastern Thailand.

The new species is named on the basis of material collected from the Phu Noi Locality, which is in the village of Ban Din Chi in the Kham Muang District of Kalasin Province, in the northeast of Thailand. Here an outcrop of the Phu Kradung Formation has produced one of the most diverse non-marine Vertebrate fossil assemblages in Southeast Asia. The Phu Kradung Formation comprises a series of sandstones, siltstones, and mudstones laid down in a fluvial environment, within a continental basin. 

Locality map and section diagram of Phu Noi Locality. (a) Map of Thailand; (b) location of Phu Noi Locality and the distribution of Phu Kradung Formation, the northeastern region with the outline of Kalasin Province; (c) diagrammatic section of Phu Noi. Nilpanapan et al. (2026).

The precise age of the Phu Kradung Formation is unknown, as it lacks any radiometrically datable horizons. However, regional stratigraphic correlations, Vertebrate assemblages, and detrital zircon data suggest that it is of Late Cretaceous origin, possibly with the uppermost part of the formation extending into the earliest Cretaceous.

The Phu Noi outcrop comprises numerous channel horizons formed within a braided river, rather than horizontal layers extending across the whole site. It has three fossil-bearing horizons. The lowest of these is a grey conglomeratic sandstone laid down in a channel bottom. About 10 m above this, the middle horizon is a brownish-purple and greenish-grey sandy siltstone and mudstone. At the same level as this, but about 400 m to the southwest, the upper horizon is a greyish siltstones within proximal floodplain deposit.

The specimen from which Nilpanpan et al. describe the new species comes from the middle horizon, which is particularly rich in Vertebrate remains, having previously yielded Hybodont Sharks,  Ginglymodian Fish, Lungfish, Eucryptodiran Turtles, Teleosaurid Crocodyliformes, and Neornithischian Dinosaurs, and with Brachyopid Temnospondyl, Rhamphorynchoidea Pterosaur, Tyrannosauroid and Metriacanthosaurid Theropod specimens currently being studied. This faunal assemblage shows a strong affinity to the Late Jurassic and earliest Cretaceous faunas of the Junggar, Turpan, and Sichuan basins of China.

The new species is named Uragasaurus kalasinensis, where 'Uragasaurus' derives from 'Uraga' (उरग) the Sanskrit word for Snake, in reference to the long, serpentine, neck of Sauropod Dinosaurs, plus '-saurus' (σαύρος), the Greek for Lizard, a common suffix in Dinosaur names, and 'kalasinensis' means 'from Kalasin' in reference to the province where the specimen was discovered. 

Uragasaurus kalasinensis is described from a single isolated anterior dorsal vertebra (PRC 460), from the Phu Noi locality, which is housed in the collection of the Palaeontological Research and Education Centre at Mahasarakham University. A number of other Sauropod elements were found close to this specimen in the same level, which Nilpanpan et al. refer to Uragasaurus kalasinensis. However, because these elements cannot be assigned to the same original Animal with 100% confidence, and they do not have overlapping diagnostic features, they are not included in the formal description of the species. This material includes two anterior dorsal neural arches (KS 34-581 & KS 34-586), a left coracoid (KS 34-587), a left fibula (KS 34-588), a middle cervical vertebra (KS 34-602a), a right cervical rib (KS 34-602b), a middle-to-posterior dorsal vertebra (KS 34-692), and a posterior dorsal vertebra (PN 13-23).

Holotype of Uragasaurus kalasinensis (PRC 460) and associated materials in the quarry map. PRC 460 Anterior dorsal vertebra in anterior view (a), KS 34-581 anterior dorsal neural arch in anterior view (b), KS 34-602a middle cervical vertebra in ventral view (c), KS 34-586 anterior dorsal neural arch in anterior view, attached by KS 34-588 fibula (d), KS 34-587 coracoid in lateral view (e), KS 34-602b right cervical rib in lateral view (f). Quarry map showing the spatial distribution of the holotype and associated materials from the Phu Noi Locality (g). PRC 460, representing the new taxon Uragasaurus kalasinensis, is indicated in red. Associated Sauropod elements include KS 34-586, KS 34-587, KS 34-588, and KS 34-602a–b, highlighted in yellow, green, blue, purple, and pink, respectively. The inset shows a close-up of the excavation grid highlighting the relative positions of the holotype and nearby associated materials. Each grid square represents 0.75 × 0.75 m. Nilpanpan et al. (2026).

The anterior dorsal vertebra assigned to Uragasaurus kalasinensis has a prominent, elongated teardrop-shaped pneumatic fossae on the distal portion of the transverse processes, intraprezygapophyseal laminae meeting ventromedially to form a Y-shaped configuration in anterior view, incorporating a single vertical intraprezygapophyseal lamina, and a shallow, subtriangular pleurocoel lacking an internal septum. 

The holotype anterior dorsal vertebra of Uragasaurus kalasinensis (PRC 460) in anterior (a) and posterior (b) views. Digital rendering of the specimen in anterior (c), posterior (d), right lateral (e), left lateral (f), dorsal (g), and ventral (h) views. Asterisk refers to an autapomorphic character. The blue highlight indicates the pneumatic fossa and pleurocoel. Abbreviations: Cpol, centropostzygapophyseal lamina; cprl, centroprezygapophyseal lamina; di, diapophysis; ns, neural  spine; pa, parapophysis; pcdl, posterior centrodiapophyseal lamina; pl, pleurocoel; pnfo, pneumatic  fossa; po, postzygapophysis; podl, postzygodiapophyseal lamina; ppdl, paradiapophyseal lamina; prdl, prezygodiapophyseal lamina; posl, postspinal lamina; prsl, prespinal lamina; spof, spinopostzygapophyseal fossa; spol, spinopostzygapophyseal lamina; sprf, spinoprezygapophyseal fossa; sprl, spinoprezygapophyseal  lamina; stprl, single interprezygapophyseal lamina; tp, transverse process; tpol, intrapostzygapophyseal lamina;  tprl, intraprezygapophyseal lamina. Nilpanpan et al. (2026).

A computed tomography of specimen PRC 460 showed that its centrum has a camellate internal pneumatic structure composed of numerous small, irregular chambers separated by thin bony septa, although it was not possible to accurately measure the dimensions of these cavities due to mineral infilling. This is a structure unique to advanced Mamenchisaurids, which differs from the procamerate internal structure seen in certain Neosauropods and the camerate condition found in Macronarians and Diplodocoids. 

Computed tomography scan of the anterior dorsal vertebra of Uragasaurus kalasinensis (holotype PRC 460). Three￾dimensional reconstructions of the vertebra in anterior view (a) and right lateral view (c). Corresponding computed tomography sections in anterior view (b) and right lateral view (d). The section plane corresponds to the dashed line separating the grey (anterior) and blue (posterior) regions in the 3D reconstructions. White boxes highlight camellate pneumatic cavities within the centrum. Red arrows indicate polygonal camellae within the camellate internal structure of the centrum. Black-and-white arrows indicate anatomical orientation in each panel. Nilpanpan et al. (2026).

Phylogenetic analysis of the taxonomic affinities of Uragasaurus kalasinensis consistently recovered the species as a basal Mamenchisaurid, although its precise placement within this group was hard to determine, which is unsurprising given the limited nature of the material. However, the same analysis consistently found Rhomaleopakhus turpanensis, a species formerly classified as being a member of the Mamenchisauridae, as being outside the group, which Nilpanpan et al. suggest may indicate the need to re-evaluate the taxonomic status of a number of Late Jurassic Asian Sauropods. 

A previous Mamenchisaurid specimen, KS26-4, was described from the Phu Dan Ma locality in 2013. This specimen comprises a nearly complete posterior cervical vertebra and two fragmentary ribs. Since this material did not contain any elements considered reliably diagnostic within the Mamenchisauridae, it was not formally described as a new species. This lack of diagnostic features, combined with a lack of shared elements with the material assigned to Uragasaurus kalasinensis leads Nilpanpan et al. to refrain from assessing whether it belongs to the same species.

Posterior cervical vertebra of Mamenchisaurus sp. from Phu Dan Ma, Kalasin Province,Thailand,Phu Kradung Formation, Late Jurassic–Early Cretaceous. Vertebra (SM KS26−4), right rib (SMKS26−2), and left rib (SMKS26−3) in anterior (A; A₂, close−up view of neural spine showing attachment scar for interspinal elastic ligament), left lateral (B), posterior (C), right lateral (D; D₂, close−up view of articular condyle showing a cancellous internal structure), and dorsal (E) views. Suteethorn et al. (2013).

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Are all known specimens of Homo naledi female?

In 2013 a large number of skeletons belonging to a previously unknown Hominin species were discovered in a newly discovered chamber within the Rising Star Cave System in the Cradle of Humankind at Maropeng, South Africa. This new chamber was named the Dinaledi Chamber (Chamber of the Stars in Sotho), and the new Hominin species was given the name Homo naledi ('naledi' meaning 'star'). A number of subsequent specimens assigned to the same species have been found in nearby chambers. Some of the specimens have been dated to between 335 000 and 236 000 years before the present, although it is possible that the total chronological range of all the specimens is longer.

Homo naledi is an unusual species, with a mosaic of modern and archaic traits. It has a small brain size, more comparable to that of an Australopithecene than an Archaic Human. The bones of the trunk and shoulders of Homo naledi also resemble those of Australopithecenes, yet the hands, lower limbs, and face of the species are far more Human. 

A recent study of the teeth of Homo naledi found that they showed remarkably little variation, and concluded that this might indicate that all known specimens might belong to a single sex. However, estimating the sex of a specimen on bone-or-tooth morphology is a remarkably difficult process, particularly where there isn't a dimorphism (i.e. two consistently different forms) within the known specimens of that species.

Sex determination can also sometimes be achieved using ancient DNA recovered from specimens. However, DNA, while this has been used on some ancient Hominins from cool climates, DNA tends to degrade rapidly in warmer environments, such as South Africa.

In a paper published in the journal Cell on 24 June 2026, a team of scientists led by Palesa Madupe of the Globe Institute at the University of Copenhagen, the Human Evolution Research Institute at the University of Cape Town, and the Max Planck Institute for Evolutionary Anthropology, present the results of a study in which they assessed the sexes of all known specimens of Homo naledi using palaeoproteomic analysis of dental enamel.

The study focuses on amelogenins, a type of protein which helps to direct the mineralisation of tooth enamel. This the DNA which is used to make this protein is principally found on the X-chromosome, however, unlike many other genes, this has not been lost from the Y-chromosome, with the effect that there are two distinct forms of amelogenin, Amelogenin X, which drives from the version of the gene on the X-chromosome, and which is produced by all Humans, and Amelogenin Y, which is derived from the version of the gene on the Y-chromosome, and which is found only in males (albeit only making up about 10% of the total. This tool has previously been used to determine the sexes of other Pleistocene Hominins, making it a realistic choice for establishing the same in Homo naledi. 

Madupe et al. began by taking surface etchings from four teeth, then processing them. All of the samples yielded the Amelogenin X variant, but none produced Amelogenin Y, indicating that all four were female. The samples were then subjected to a more destructive round of testing, crushing the teeth completely and then analysing the whole sample. This yielded identical results, indicating that the less destructive test was sufficiently reliable.

Location and layout of the Rising Star cave system. (A) Map of South Africa zoomed in (insert), showing the position of the area known as the Cradle of Humankind, approximately 50 km northwest of Johannesburg, where the Rising Star cave system is located. (B) The Rising Star cave system within the Cradle of Humankind. (C) Layout of the Rising Star System and the Dinaledi subsystem and Lesedi Chamber, where all the specimens were recovered, and the photos of the four Homo naledi specimens initially micro-destructively sampled by acid etching, then sectioned for enamel growth analysis and subsequently sampled destructively. Madupe et al. (2026).

Following this success, Madupe et al. carried out an analysis of another nineteen Homo naledi teeth, using the non-destructive method (i.e. using surface etchings, not whole teeth). This included all 20 known Homo naledi specimens within the experiment. The Amelogenin X variant was again found in seventeen specimens, while the Amelogenin Y variant was again not detected. Two specimens yielded such low protein levels that they were excluded from the study, although these specimens also yeilded Amelogenin X variant at low levels and no Amelogenin Y variant. The Amelogenin Y variant was detected in all the controls used for the study, which comprised fifteen male Homo sapiens, two male Paranthropus robustus, a male Australopithecus africanus, a male Denisovan, and a male Homo antecessor. 

The Amelogenin X protein found in Homo naledi showed no variation, something which would be considered extra-ordinary in a modern Human population, suggesting that either the species Homo naledi was remarkably genetically homogeneous, or that all of the individuals were very closely related. The individuals come from locations up to 145 m from one another within a complex cave system, and are not thought to have been deposited at the same time, making the former diagnosis more likely.

Madupe et al. identify eighteen confidently identified informative single amino acid polymorphisms on the Hominid Amelogenin X protein, two of which are notably different in Homo naledi and Modern Humans. One of these, a phenylalanine amino acid molecule at position 141 on the protein, is the same as that seen in present day Strepsirrhini (Lemurs, Galagos, Pottos, and Lorises) and Cercopithecidae (Old World Monkeys), but differs from the position in Modern Humans, Neanderthals, and Denisovans, all of which have a tyrosine amino acid at this point. The second, a proline amino acid at position 635, is the same character state as in all living non-Human Primates, but differs from the situation in Modern Humans, Neanderthals, and Denisovans, all of which have an alanine amino acid at this point. This location has not been recovered in any Homo antecessor, Homo erectus, or Australopithecus africanus specimen to date, but has been identified in two Paranthropus robustus specimens, both of which both had a proline amino acid in this position.

Analysis of the Amelogenin protein has previously been shown to be a useful way to identify the sex of a variety of Pliocene and Pleistocene Hominins. Application of this test to Homo naledi failed to identify any males among the 20 individuals currently known, nor any intra-specific variation on the protein, both highly unusual states. Notably, the study included individual UW 102a, popularly known as 'Neo' (pronounced ney-oh), the most complete Homo naledi specimen known, who has previously identified as male on the basis of a relatively robust skeleton (fortunately, the name Neo, which is Sotho and means 'gift', can be applied to either sex). 

The cranium of Homo naledi specimen popularly known as 'Neo'. Nutcracker Man.

Since the method has previously been applied to individuals from South Africa as much as two million years old, and all of the male controls used within the study were identified as such, Madupe et al. do not believe there was anything wrong with the methodology being used. On this basis, they conclude that the Amelogenin Y variant was not present in any of the specimens, either because they were all female, or because of a mutation which prevented the expression of this protein in male Homo naledi. However, if the previous study on the dentition of Homo naledi is taken into account, it does raise the likelihood of all specimens being female.

Mutations which lead to the deletion or non-expression of the Amelogenin Y protein are known. They are more common in some Human populations than others (in one population in Pakistan, 8% of men did not produce this protein), and has been observed in a Neanderthal individual from Siberia. However, such mutations are typically extremely rare. 

Since there is no reason to believe the sex ratio in living Homo naledi populations was anything other than 1:1, a random accumulation of 20 female specimens is incredibly unlikely. However, such a ratio is not inconsistent with the previously-made suggestion that the presence of Homo naledi specimens in the Rising Star Cave System may have been the result of deliberate mortuary practices rather than a random accumulation. 

The Dinaledi Chamber is notoriously hard to access, to the extent that following its discovery, lead scientist Lee Berger assembled a team of physically small female palaeontologists and archaeologists with caving experience in order to carry our excavation work there. In theory, the cave could have been equally inaccessible to male Homo naledi, leading to a bias in the preservation of individuals there. However, ten of the known individuals are juveniles who died before their second molar erupted, an age at which it is unlikely that sex-related size-differences would have been sufficient to prevent males entering the site.

Exclusively female funerary sites are not known from any Modern Human population. The closest we have are the Neolithic Panoría site in Spain and Edcoural Cave site in Portugal, where females make up 70% and 67% of the population respectively, something which has been thought to reflect the greater importance of females in a matrilineal society. However, the Neolithic inhabitants of Iberia were still Modern Humans, very different to Homo neledi, a Pleistocene Hominin not interpreted to have been closely related to us, and the two groups cannot be expected to have had similar funerary practices (if Homo naledi indeed had these at all).

The expression of archaic amino acid variants in Homo naledi further supports the idea that this species was not closely related to Modern Humans, although the absence of data from archaic Homo species, such as Homo erectus or Homo antecessor, makes it hard to work out how distant a relationship this implies. Gathering such data for more Human and Australopithecene species may help to resolve the phylogentic position of Homo naledi. The less destructive sampling method used by Madupe et al. in this study should make such sampling easier that the earlier form of this technique, which required the destruction of whole teeth, a highly precious resource for extinct Hominins.

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Bryozoans from the Early Cambrian Cambrian Xiannüdong Formation of Shaanxi Province, China.

Molecular clock studies have suggested that the Phylum Bryozoa, or Moss Animals, first appeared in the Early Cambrian, which is consistent with the appearance of nearly all other Animal phyla at this time. However, for a long time the earliest known fossil Bryozoans came from the Early Ordovician, at which point six of the eight known orders of Bryozoans appear abruptly. Several putative Cambrian Bryozoan fossils, such as Pywackia, Archaeotrypa, and Marcusodictyon, were described, but none of these was universally accepted as a Bryozoan. In 2021 a more plausible Brozoan, Protomelission gatehousei, was described from the Early Cambrian of Australia and South China. In this it was possible to identify several Brozoan traits, including monomorphic zooid capsules, modular construction, organic composition, and a simple linear budding growth geometry, leading to the conclusion that this was probably a stem-group Bryozoan.

Protomelission gatehousei from the Cambrian Wirrealpa Limestone, South Australia. (a)–(g) Holotype, SADME 10470. (a) Front side of the colony showing the seven series of zooids. Top box corners indicate the area shown in (f); bottom box corners show the broken-off part in (c). (b) The top broken part of (a). (c) The lower broken part of (a). (d) Oblique lateral view of the bilaminate colony. (e) Enlarged view of (d) showing the staggered budding pattern and the curved basal walls of the two back-to-back layers (arrows and tailed arrows) in the bifoliate colony. (f) Quincuncial arrangement of sub-hexagonal zooids with broken frontal walls. (g) Lateral view of uncovered zooids; note the minute spoon-shaped structure (arrow) at the proximal end of basal wall extending backwards underneath the distal part of the parent zooid. (h), (i) SADME 10470-2. (h) Lateral view of a broken colony, showing the largely broken frontal walls (tailed arrows) and basal walls of opposite layer (arrows). (i) Enlarged view of three adjacent zooids. Note the dome shape of the distal part of frontal wall (tailed arrows), and almost circular orifice of zooid. Abbreviations: B, basal wall; F, frontal wall. Zhang et al. (2021).

However, while Protomelission gatehousei shows enough Bryozoan-like features that most palaeontologists have accepted it to be at least a stem group Bryozoan, the specimens used to describe the species lacked the definitive Bryozoan soft-tissue anatomy and diagnostic skeletal microstructure which would be necessary for complete conformation, leaving the identity of these fossils open to challenge.

In a paper published in the journal Nature on 3 June 2026, Baopeng Song (宋宝鹏) and Zhifei Zhang (张志飞) of the Department of Geology at Northwest University, Luke Strotz, also of the Department of Geology at Northwest University and also of the Department of Earth Sciences at Utrecht University, Timothy Topper, again of the Department of Geology at Northwest University, and of the Department of Palaeobiology at the Swedish Museum of Natural History, Andrej Ernst of the Institut für Geologie at Universität Hamburg, Zhiliang Zhang of the Department of Geology at Northwest University, and the Institut für Geologie at Universität Hamburg, Mei Luo (罗梅), again of the Department of Geology at Northwest University, Lars Holmer, again of the Department of Geology at Northwest University, and of the Department of Earth Sciences at Uppsala University, Yue Liang (梁悦), Yazhou Hu (胡亚洲), Caibin Zhang (张彩彬), and Yanlong Chen (陈延龙), all of the Department of Geology at Northwest University, and Glenn Brock, once again of the Department of Geology at Northwest University, and of the School of Natural Sciences at Macquarie University, describe new specimens of Protomelission gatehousei from the Early Cambrian Xiannüdong Formation of southern Shaanxi Province, China, as well as a second new species of Bryozoan from the same formation.

Notably, these fossils preserve soft-tissue features in exceptional fidelity, including internal moulds of membranous sacs in the zooid chambers, which allow the unequivocal placement of these taxa within the Phylum Bryozoa. The presence of two separate Bryozoan taxa within these Early Cambrian deposits pushes the origin of the group still earlier, confirming that this group appeared during the Cambrian explosion.

Specimen of Protomelission gatehousei from the Xiannüdong Formation in which the membranous sacs are preserved (ELI DYCX 8-001). (a) Front side of the colony. The outlined area is magnified in (h). (b) Back side of the colony. The outlined area is magnified in (j). (c) Lateral view of the bifoliate colony. (d) Oblique lateral view of the bifoliate colony showing the hollow arched mesotheca (arrow). (e) Partial enlargement of (c) showing the staggered budding pattern. (f), (g) X-ray tomographic microscopy images showing the longitudinal section of the colony and the orifice of autozooids (arrowheads) (f, oblique lateral view; (g) lateral view). (h) Quincuncial arrangement of sub-hexagonal membranous sacs with elliptical orifice. Note the 10-μm gap present between adjacent membranous sacs, indicating the loss of skeletal walls during the taphonomic processes. The outlined area is the membranous sac magnified in (i). (i) Enlarged view of a membranous sac showing the orifice (asterisk), circular fibres (arrow) and longitudinal fibres (arrowhead). These features suggest muscle preservation in the membranous sac. (j) Enlarged view of a zooid. Note that the aperture is coated with secondary phosphate. (k) Enlarged view of a zooid. Note that the secondary phosphate coating of the aperture is partially stripped away. (l), (m) Enlarged view of the membranous sac showing the longitudinal fibres in (l) arrowhead, and circular fibres in (m), arrow. These features suggest muscle preservation in the membranous sac. Scale bars, 500 μm (a)–(d), 50 μm (e), (i)–(k), 200 μm (f), 150 μm (g), 100 μm (h) and 30 μm (l), (m). Song et al. (2026).

These new specimens show Protomelission gatehousei as forming upright colonies with two curved lamellar sheets of zooids back-to-back, with the largest colonies being 1-2 mm in width and about 3 mm high, tapering towards their tip. Each of these lamellae has six-to-eight rows of zooids, with budding originating from a planar mesotheca.

Soft-tissue preservation of Protomelission gatehousei. (a)–(e) ELI DYCX 8-005. (a) Front side of the colony, box corners indicate the area shown in (d). (b) The back side of the colony. (c) Lateral view of the bifoliate colony. (d), (e) Enlarged view of elongated hexagonal zooids. Note the longitudinally neatly arranged cylindrical structures on the both sides of the ridge-like orifice, which are possible secondary coatings of protective shields. (f) Protective shields developed in an extant Cheilostome Bryozoan, Valdemunitella sp. photographed by Dennis Gordon (Wellington). Song et al. (2026).

The new species described is named Dayingomelission hexaclitia, where 'Dayingomelission' means 'honeycomb from Daying' and 'hexaclitia' means 'six slopes' in reference to the sloped, hexagonal apertures of its autozooids. Colonies of Dayingomelission hexaclitia form a sheet-like grown covering the substrate. This sheet is interpreted as having spread by linear branching, with a single row of zooids diverging to form two new rows. Each autozooid is hexagonal and box-like, between 200 µm to 400 µm in diameter, and separated from its neighbours by a double-walled structure. All vertical walls show this double-walled structure, while the basal wall is planar, sometimes showing a slight curvature. 

Specimens of Dayingomelission hexaclitia from the Xiannüdong Formation showing the colony and cystids. (a), (b) ELI ZJBX 10-001 (holotype). (a) Oblique view of the front side of a unilaminate colony form clearly showing the regular hexagonal, compactly arranged, honeycomb-shaped cystids. The outlined area is shown in (b). (b) Hexagonal cystid with vertical wall and ring septa clearly evident (arrow). (c)–(e) ELI ZJBX 10-002. (c) Front side of a unilaminate colony form. The bottom outlined area shows the cystids magnified in (d); whereas the top outline shows the cystids magnified in (e). (d) Enlarged view of adjacent cystids. Note the hexagonal vertical wall (arrow) and the basal exterior wall of cystids (arrowheads). (e) Row bifurcation showing change in zooid width along rows. (f)–(i) ELI ZJBX 3-001. (f) Front side of a unilaminate colony form with styles indenting the zooidal chambers. (g) Oblique view showing hexagonal cystids with styles. (h) Oblique view of colony surface. Note that the styles arise in the endozone and extend through most of exozone. (i) Enlarged view of the vertical wall with planar spherulitic fabric. Scale bars, 500 μm (a), (c), 80 μm (b), 100 μm (d), 200 μm (e), 300 μm (f), (g), 100 μm (h) and 25 μm (i). Song et al. (2026).

Both species have hexagonal zooids with a box-shaped profile and a non-porous phosphatized or silicified skeleton. These are more-or-less uniform in size, and angled at 30-75° to the median lamina or basal exterior wall. They have preserved phosphatized internal structures interpreted as membranous sacks, the outer end of which comprises an elliptical orifice surrounded by an undulating fold. These are made up of densely packed circular and longitudinal fibres interpreted as annular and longitudinal muscles. Longitudinally aligned cylindrical structures, possibly representing protective shields or a broad operculum are present in some specimens. In others sac is attached to the cystid wall in the inner part of the zooid cell.

Membranous sacs preserved in situ in the autozooid cystids of Protomelission gatehousei and Dayingomelission hexaclitia and colonial growth reconstruction of Protomelission gatehousei . (a), (b) Protomelission gatehousei  ELI DYCX 8-016. (a) Front side of a bifoliate colony showing the eight series of zooids. The outlined area is magnified in (b). (b) Enlarged view of a zooid. Note that the membranous sac (arrow) is preserved in the cystid (arrowhead). (c)–(g) Dayingomelission hexaclitia ELI DYCX 8-004. (c) Front side of a unilaminate colony, with ten series of zooids, all with membranous sacs and cystids. The outlined area is magnified in (g). (d) Back side of the colony showing the membranous sacs of the zooids and the gap between the sacs. The outlined area is magnified in (e). (e) Enlarged view showing capsule￾like membranes and gaps. (f) X-ray tomographic microscopy image showing the longitudinal section of zooids with membranous sacs and cystids. (g) Enlarged view highlighting that the membranous sacs (arrow) are captured in the cystids (arrowhead), and the membranous sacs are in contact with the cystids 20 μm from the apertures (ligamentous attachment, asterisks). (h) Three-dimensional reconstruction of a Bryozoan zooid with protruding lophophore. (i) Longitudinal section of reconstructed Bryozoan zooid. Greyish white, cystid; translucent white, membranous sac and tentacles; pink, polypide excluding tentacles. (j) Reconstruction of Protomelission gatehousei , front surface view. Scale bars, 500 μm (a), (c), (d), 40 μm (b), 200 μm (e), (f) and 100 μm (g). Song et al. (2026).

Both Protomelission gatehousei and Dayingomelission hexaclitia show most of the key features associated with Palaeozoic Bryozoans, including  aspects of their colony morphology, their skeletal architecture,  the presence of soft-tissue structures such as membranous sacs, as well as annular and longitudinal musculature. Notably they contain a number of features associated with the Class Stenolaemata, including styles and  a free-walled colony organisation, which would make both species crown-group Brozoans. This makes it more likely that they were biomineralized in life, although it is impossible to determine the initial composition of their skeletons. Brozoans are known to have undergone a number of independent biomineralization events, with a molecular clock analysis indicating that the first of these was likely to have happened in the Early Cambrian. These results also imply that the common ancestor of the organic￾walled Gymnolaemata and the mineralized Stenolaemata probably originated in the early Cambrian (Terreneuvian) or even perhaps in the Ediacaran Period.

Phylogenetic relationships of Bryozoans. A 50% majority-rule consensus phylogenetic tree inferred using morphological characters and Bayesian analysis based on a matrix of 22 taxa and 50 characters. Node values are Bayesian posterior probability support values. Coloured areas indicate the three taxonomic classes that comprise the Bryozoa along with outgroups, with Protomelission and Dayingomelission belonging to Stenolaemata. Song et al. (2026).

The presence of two species of Bryozoan in the Early Cambrian Xiannüdong Formation of Shaanxi Province, as well as one of these species being present in the lower Wirrealpa Limestone of South Australia makes it likely that Bryazoans had already diversified and become widespread in the Early Cambrian. This lends support to the idea that the tentative mineralised Bryomorphs from the Lower Cambrian of Nevada recently described by Pruss et al. (2022) are also Bryozoans, and that Moss Animals were therefore widespread in shallow Cambrian seas, particularly Archaeocyath reef-associated carbonate platform settings. 

See also...